The Immunotoxicity of Workplace Xenobiotics interagency agreement functions to enhance the immunotoxicological evaluations of humans exposed to quantifiable levels of xenobiotics in the environment and workplace. Personal exposure to fungal bioaerosols and other mold related xenobiotics from contaminated building materials in the home or school environment is of growing concern in the general population, particularly in pediatric populations. In epidemiological studies, the inhalation of fungal spores, hyphae, and fragments has been associated with exacerbations of respiratory morbidity such as asthma, allergic rhinitis, and hypersensitivity pneumonitis. Certain occupational populations are also at elevated risk for fungal exposures including agriculture and horticultural workers that handle contaminated farm and bio-waste products in agricultural facilities, wood processing workers, as well as construction and remediation workers that handle contaminated building materials. Although fungal exposure has often been associated with allergic, toxic and/or infectious health effects, the actual potential of different fungi to exacerbate these adverse effects remains unclear. The National Academy of Sciences has recognized the need to develop better fungal exposure assessment methods as a high research priority. The NTP also has a major initiative for studying the health effects of fungal exposure. Personal exposure to airborne fungi and other fungal related xenobiotics has been associated with a variety of adverse health effects ranging from systemic and opportunistic infections, allergies, asthma, to toxic reactions. However, not all fungi are equally important and improved diagnostics are essential to develop informative exposure and surveillance techniques. The projects conducted as part of this interagency agreement support the NTP mission through the development of analytical reagents for improved species-specific identification of fungi and to better evaluate the health effects associated with fungal exposures. The knowledge gained from these projects will assist in the development of improved testing methods for the quantification of environmental fungi, as well as generate data that will strengthen the scientific base for fungal exposure risk assessment. These projects will additionally address specific NIOSH and NIEHS research goals for reducing environmental and occupational causes or contributing factors to acute and chronic illness and disease in worker populations as well as children.